POS-Seal Tips, black butyl rubber gasket with 3 mm pore for sealing the POS (sensor head) against the O2k-Chamber. Push the wetted POS-Seal Tip over the POS-sensor head, with the pore positioned centrally, not covering any peripheral area of the gold cathode. Do not stretch the gasket across the POS-sensor head.
One pack (4 seal tips) of this product is a standard component of the POS-Service Kit.